The effect of AZT and interferon on the replication of HIV-1 was evaluated by PCR. Briefly, H9 and U937 cells were infected with cell-free HIV-1, after which the drugs were added at the indicated concentrations, AZT 50 ug/ml, rIFNa at 50U/ml or in combination at the same concentrations. At various time points after infection cells were harvested and genomic DNA and RNA prepared for analysis of viral nucleic acid by PCR. Both DNA and RNA were amplified using primers to the gag region (SK38/39). Virus productions was measured by reverse transcriptase (RT) and p24 antigen assays. Greater that 95% inhibition of HIV replication was observed with AZT and the combination of AZT and rIFNa from 3-4 days after infection using the p24 and RT assays in both the H9 and U937 cells. Viral DNA and RNA synthesis were not significantly inhibited by rIFNa. Some inhibition of DNA and RNA was observed with AZT alone followed by recovery of viral nucleic acid with time. More than 80% inhibition of viral DNA synthesis was observed with the combination of AZT and rIFNa. Viral RNA was undetectable in both infected H9 and U937 cells in the presence of AZT and rIFNa combined our results suggest that combination therapy with AZT and RIFNa may be more effective for sustained inhibition of virus such as AZT and ddC, ddC and RIFNa and ddC, rIFNa and AZT on HIV-1 replication in infected H9 and U937 cells. The molecular mechanism of this inhibitory effect will be studied by analyzing the expression of various hot genes in response to drug treatment. This work has been accepted for a poster presentation at the Cold Spring Harbor meeting on Vaccines.